Diquat associated with copper sources for algae control: Efficacy and ecotoxicology
2016
Garlich, Nathalia | Da Cruz, Claudinei | Da Silva, Adilson F. | Carraschi, Silvia P. | Malaspina, Igor C. | Pitelli, Robinson A. | Bianco, Silvano
ABSTARCT The aims of this research were to evaluate the efficacy of copper oxychloride (CuCl ₂.3Cu(OH) ₂), copper hydroxide (Cu(OH) ₂) and diquat (1.1′-ethylene-2.2′-bipyridyldiylium dibromide), isolated and in association with 0.1% of both copper sources, in the control of the unicellular algae Ankistrodesmus gracilis and the filamentous algae Pithophora kewesis , and to determine the acute toxicity of the tested chemicals in Hyphressobrycon eques, Pomacea canaliculata, Lemna minor and Azolla caroliniana. The efficacy was estimated by the methods of chlorophyll a and pheophytin a readings, changed into growth inhibition percentage. Both algae were exposed to the following concentrations: 0.2; 0.4; 0.8; 1.2 mg L ⁻¹ of diquat and its association with the copper sources; and 0.1; 0.3; 0.5; 0.7; 1.0 and 1.5 mg L ⁻¹ in the isolated applications of copper hydroxide and copper oxychloride. An untreated control was kept. The acute toxicity was estimatedby 50% lethal concentration (LC50). The copper sources were effective for A. gracilis control, at rates as high as 0.1 mg L ⁻¹ (>95% efficacy). Isolated diquat and its association with copper hydroxide were both effective at rates as high as 0.4 mg L ⁻¹, with 95 and 88% control efficacy, respectively. The copper oxychloride was effective at 0.2 mg L ⁻¹, with 93% efficacy. None of the tested chemicals and associations was effective on P. kewesis control. The most sensitive non target organism to the tested chemicals was L. minor ; the less sensitive was H. eques.
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